149 lines
4.1 KiB
C
149 lines
4.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2016 Trond Myklebust
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*
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* I/O and data path helper functionality.
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/bitops.h>
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#include <linux/rwsem.h>
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#include <linux/fs.h>
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#include <linux/nfs_fs.h>
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#include "internal.h"
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/* Call with exclusively locked inode->i_rwsem */
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static void nfs_block_o_direct(struct nfs_inode *nfsi, struct inode *inode)
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{
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if (test_bit(NFS_INO_ODIRECT, &nfsi->flags)) {
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clear_bit(NFS_INO_ODIRECT, &nfsi->flags);
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inode_dio_wait(inode);
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}
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}
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/**
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* nfs_start_io_read - declare the file is being used for buffered reads
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* @inode: file inode
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*
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* Declare that a buffered read operation is about to start, and ensure
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* that we block all direct I/O.
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* On exit, the function ensures that the NFS_INO_ODIRECT flag is unset,
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* and holds a shared lock on inode->i_rwsem to ensure that the flag
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* cannot be changed.
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* In practice, this means that buffered read operations are allowed to
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* execute in parallel, thanks to the shared lock, whereas direct I/O
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* operations need to wait to grab an exclusive lock in order to set
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* NFS_INO_ODIRECT.
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* Note that buffered writes and truncates both take a write lock on
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* inode->i_rwsem, meaning that those are serialised w.r.t. the reads.
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*/
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void
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nfs_start_io_read(struct inode *inode)
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{
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struct nfs_inode *nfsi = NFS_I(inode);
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/* Be an optimist! */
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down_read(&inode->i_rwsem);
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if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0)
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return;
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up_read(&inode->i_rwsem);
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/* Slow path.... */
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down_write(&inode->i_rwsem);
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nfs_block_o_direct(nfsi, inode);
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downgrade_write(&inode->i_rwsem);
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}
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/**
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* nfs_end_io_read - declare that the buffered read operation is done
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* @inode: file inode
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*
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* Declare that a buffered read operation is done, and release the shared
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* lock on inode->i_rwsem.
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*/
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void
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nfs_end_io_read(struct inode *inode)
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{
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up_read(&inode->i_rwsem);
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}
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/**
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* nfs_start_io_write - declare the file is being used for buffered writes
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* @inode: file inode
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*
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* Declare that a buffered read operation is about to start, and ensure
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* that we block all direct I/O.
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*/
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void
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nfs_start_io_write(struct inode *inode)
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{
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down_write(&inode->i_rwsem);
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nfs_block_o_direct(NFS_I(inode), inode);
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}
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/**
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* nfs_end_io_write - declare that the buffered write operation is done
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* @inode: file inode
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*
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* Declare that a buffered write operation is done, and release the
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* lock on inode->i_rwsem.
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*/
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void
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nfs_end_io_write(struct inode *inode)
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{
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up_write(&inode->i_rwsem);
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}
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/* Call with exclusively locked inode->i_rwsem */
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static void nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode)
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{
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if (!test_bit(NFS_INO_ODIRECT, &nfsi->flags)) {
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set_bit(NFS_INO_ODIRECT, &nfsi->flags);
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nfs_sync_mapping(inode->i_mapping);
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}
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}
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/**
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* nfs_end_io_direct - declare the file is being used for direct i/o
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* @inode: file inode
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*
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* Declare that a direct I/O operation is about to start, and ensure
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* that we block all buffered I/O.
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* On exit, the function ensures that the NFS_INO_ODIRECT flag is set,
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* and holds a shared lock on inode->i_rwsem to ensure that the flag
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* cannot be changed.
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* In practice, this means that direct I/O operations are allowed to
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* execute in parallel, thanks to the shared lock, whereas buffered I/O
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* operations need to wait to grab an exclusive lock in order to clear
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* NFS_INO_ODIRECT.
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* Note that buffered writes and truncates both take a write lock on
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* inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT.
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*/
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void
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nfs_start_io_direct(struct inode *inode)
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{
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struct nfs_inode *nfsi = NFS_I(inode);
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/* Be an optimist! */
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down_read(&inode->i_rwsem);
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if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) != 0)
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return;
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up_read(&inode->i_rwsem);
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/* Slow path.... */
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down_write(&inode->i_rwsem);
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nfs_block_buffered(nfsi, inode);
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downgrade_write(&inode->i_rwsem);
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}
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/**
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* nfs_end_io_direct - declare that the direct i/o operation is done
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* @inode: file inode
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*
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* Declare that a direct I/O operation is done, and release the shared
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* lock on inode->i_rwsem.
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*/
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void
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nfs_end_io_direct(struct inode *inode)
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{
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up_read(&inode->i_rwsem);
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}
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